type Pipe struct {
	Sender              Sender
	Receiver            Receiver
	OnReceiveCompletion func()
	OnSendCompletion    func()
}

type Receiver interface {
	Receive() bool
	Cancel()
	Status() Status
	Request() interface{}
}

type Request struct {
	Payload  interface{}
	Canceled bool
}

type Sender interface {
	Request() Request
	Update(v interface{})
	Finalize(v interface{}, err error)
	Status() Status
}

type Status struct {
	Canceled  bool
	Completed bool
	Err       error
	Value     interface{}
}